1. Technical Field
The present disclosure relates to a method for producing an electrolytic capacitor, and, in detail, relates to a method for producing an electrolytic capacitor having a solid electrolyte layer.
2. Description of the Related Art
Along with digitalization of electronic devices, small-sized and large capacitance capacitors, which are used in the electronic devices, having low equivalent series resistance (ESR) in a high frequency range have been demanded.
Conventionally, plastic film capacitors, laminated ceramic capacitors, and the like have been used as capacitors for a high frequency range in many cases, however, these capacitors have relatively small capacitance.
Promising candidates as small-sized, large capacitance, and low ESR capacitors are electrolytic capacitors including as a cathode material a conductive polymer such as polypyrrole, polythiophene, polyfuran, or polyaniline. For example, a capacitor element that includes a dielectric layer-formed anode foil, and a solid electrolyte layer including a conductive polymer as a cathode material, which is provided on the anode foil, is proposed.
However, there is a problem that the conductive polymer reacts with moisture to decrease electric conductivity, causing, for example, a decrease in electrostatic capacity and an increase in ESR. In order to solve the problem, it is reported that the solid electrolyte layer is formed with use of a conductive polymer solution containing, together with the conductive polymer, a water-soluble polyhydric alcohol and an oxoacid such as boric acid (see WO 2012/137969 A).
In addition, with regard to the capacitor provided with the solid electrolyte layer, an electrolyte solution containing a polyhydric alcohol, boric acid, and the like has been conventionally used to enhance self-restoration performance and thus improve a withstand voltage (see Unexamined Japanese Patent Publication No. H11-283874).